Chip-scale electronic package structure with conductive connective element having increased surface area and laterally spaced connection points for improved connectivity

ABSTRACT

An electronic package includes a lead frame structure having one or more structural features configured to improve board level reliability. In one embodiment, the structural feature comprises lead frame protrusions extending outward from the electronic package, which are configured to laterally engage solder structures used to attach the electronic package to a next level of assembly. In another embodiment, conductive bumps are attached to exposed portions of the lead frame in advance of next level assembly processes. In a further embodiment, the lead frame comprises laterally separated contact points for attaching an electron die and for attaching the electronic package to a next level of assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No. 10-2015-0029706 filed on Mar. 3, 2015 in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference.

BACKGROUND

The present invention relates, in general, to electronics, and more particularly, to semiconductor packages, structures thereof, and methods of forming semiconductor packages.

Electronic devices, such as semiconductor dies are conventionally enclosed in package structures that protect the semiconductor die from hostile environments and that enable electrical interconnection between the semiconductor die and a next level of assembly, such as a printed circuit board (“PCB”) or motherboard. The elements of a typical package structure include a conductive leadframe or substrate, an integrated circuit or semiconductor die, conductive structures, such as bond wires or solder balls that electrically connect pads on the semiconductor die to individual leads of the leadframe or substrate, and a hard plastic encapsulant material that covers the other components and forms an exterior of the semiconductor package commonly referred to as the package body. Portions of the individual leads are configured to electrically connect the package structure to the next level assembly.

In the past, certain reliability issues have plagued packaged electronic devices particularly in chip-scale packaged electronic devices having a high density of interconnects in a small footprint package. Such reliability issues have included, for example, poor bonding between the package electronic device and solder materials used to connect the packaged electronic device to a next level assembly and as well as other stress induced failures.

Accordingly, it is desirable to have a structure and method for forming packaged electronic devices that reduce the occurrence of reliability issues, such as those described previously. It is further desirable for the structure and method to be cost effective and manufacturable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a cross-sectional view of an electronic package in accordance with an embodiment of the present invention;

FIG. 1B illustrates a cross-sectional view of the electronic package of FIG. 1A attached to a next level of assembly in accordance with an embodiment of the present invention;

FIG. 2A illustrates a cross-sectional view of an electronic package in accordance with another embodiment of the present invention;

FIG. 2B illustrates a cross-sectional view of the electronic package of FIG. 2A attached to a next level of assembly in accordance with an embodiment of the present invention;

FIG. 3A illustrates a perspective plan view of an electronic package in accordance with a further embodiment of the present invention; and

FIG. 3B illustrates a partial cross-sectional view of the electronic package of FIG. 3A taken along reference line 1-1′ of FIG. 3A attached to a next level of assembly in accordance with an embodiment of the present invention.

For simplicity and clarity of illustration, elements in the figures are not necessarily drawn to scale, and the same reference numbers in different figures denote generally the same elements. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. In addition, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, numbers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and/or groups thereof. It will be understood that, although the terms first, second, etc. may be used herein to describe various members, elements, regions, layers and/or sections, these members, elements, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one member, element, region, layer and/or section from another. Thus, for example, a first member, a first element, a first region, a first layer and/or a first section discussed below could be termed a second member, a second element, a second region, a second layer and/or a second section without departing from the teachings of the present disclosure. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. It will be appreciated by those skilled in the art that words, during, while, and when as used herein related to circuit operation are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as propagation delay, between the reaction that is initiated by the initial action. Additionally, the term while means a certain action occurs at least within some portion of a duration of the initiating action. The use of word about, approximately or substantially means a value of an element is expected to be close to a state value or position. However, as is well known in the art there are always minor variances preventing values or positions from being exactly stated. Unless specified otherwise, as used herein the word over or on includes orientations, placements, or relations where the specified elements can be in direct or indirect physical contact. Unless specified otherwise, as used herein the word overlapping includes orientations, placements, or relations where the specified elements can at least partly coincide or align in the same or different planes. It is further understood that the embodiments illustrated and described hereinafter suitably may have embodiments and/or may be practiced in the absence of any element that is not specifically disclosed herein.

DETAILED DESCRIPTION OF THE DRAWINGS

The present description includes, among other features, an electronic package structure comprising a substrate. The substrate includes a lead frame configured with one or more structural features configured to improve board level reliability of the electronic package. In one embodiment, the lead frame includes protrusions that extend outward from a surface of the electronic package. The protrusions are configured to laterally engage conductive connective structures, such as solder balls. In another embodiment, conductive bumps are attached to exposed portions of the lead frame in advance of attaching the electronic package structure to a next level of assembly. In a further embodiment, the lead frame is configured with different points of contact for attaching an electronic die to the lead frame and for attaching the lead frame to the next level of assembly. More particularly, the points of contact are laterally separated from each other to, among other things, reduce the vertical concentration of stress regions in the electronic package structure.

In one embodiment, the electronic package structure comprises a substrate. The substrate comprises a die pad having a die pad top surface and an opposing die pad bottom surface, wherein the die pad comprises a conductive material. A plurality of leads are laterally spaced apart from the die pad, and a substrate encapsulant is interposed between the die pad and the plurality of leads, wherein the substrate encapsulant has a substrate top surface and an opposing substrate bottom surface, and wherein the die pad and plurality of leads protrude outward from the substrate bottom surface. An electronic die is electrically coupled to the die pad and the plurality of leads and a package body encapsulates the electronic die and the substrate top surface, wherein the substrate bottom surface is exposed to the outside.

In another embodiment, the electronic package comprises a substrate. The substrate comprises a die pad having a die pad top surface and an opposing die pad bottom surface, wherein the die pad comprises a conductive material. A plurality of leads is laterally spaced apart from the die pad, each lead having a lead top surface and an opposing lead bottom surface. A substrate encapsulant is interposed between the die pad and the plurality of leads, wherein the substrate encapsulant has a substrate top surface and an opposing substrate bottom surface. Conductive bumps are disposed on the die pad bottom surface and the lead bottom surfaces. An electronic die is electrically coupled to the die pad and the plurality of leads and a package body encapsulating the electronic die and the substrate top surface, wherein the substrate bottom surface is exposed to the outside. In one embodiment, the die pad bottom surface and lead bottom surfaces can be substantially co-planar with the substrate bottom surface.

In a still further embodiment, the electronic package structure comprises a substrate including a die pad and a plurality of leads spaced apart from the die pad. An electronic die is electrically connected to the die pad and the plurality of leads. an encapsulant structure encapsulating the substrate and the electronic die, wherein a bottom surface of the die pad and bottom surfaces of the plurality of leads are exposed to the outside, wherein the electronic die is attached to first portions of the plurality of leads to define first connection points, and wherein the plurality of leads comprise second portions attached to the first portions, wherein the second portions are configured to define second connection points for attaching to a next level of assembly, and wherein the first connection points and the second connection points are laterally separated.

In a still further embodiment, an electronic package structure comprises a substrate, which comprises a die pad having die pad top surface and an opposing die pad bottom surface, wherein the die pad comprises a conductive material, a plurality of leads laterally spaced apart from the die pad each lead having a lead top surface and an opposing lead bottom surface, and a substrate encapsulant interposed between the die pad and the plurality of leads, wherein the substrate encapsulant has a substrate top surface and an opposing substrate bottom surface. An electronic die electrically coupled to the die pad and the plurality of leads, and a package body encapsulating the electronic die and the substrate top surface, wherein the substrate bottom surface is exposed to the outside. The substrate further comprises one or more structural features configured to improve board-level reliability, the one or more features comprising one or more of: the die pad and the plurality of leads configured to protrude outward from the substrate bottom surface such that side surfaces of the die pad and side surfaces of the plurality of leads are exposed to the outside, conductive bumps disposed on the die pad bottom surface and the lead bottom surfaces, and/or at least one lead comprising a first lead portion exposed to the outside of the substrate bottom surface and defining a first connection point for attaching the electronic package structure to a next level of assembly, and a second lead portion laterally extending towards the die pad and having a recessed bottom surface encapsulated by the substrate encapsulant, the second lead portion defining a second connection point for attaching to the electronic die, wherein the first connection point is laterally separated from the second connection point.

Various aspects of the present description can be embodied in different forms and should not be construed as being limited to the example embodiments set forth herein. Rather, these example embodiments of the disclosure are provided to convey various aspects of the disclosure to those of ordinary skill in the art.

FIG. 1A illustrates a cross-sectional view of an electronic package 100 or electronic package structure 100, such as a semiconductor package 100, in accordance with a first embodiment. FIG. 1B illustrates a cross-sectional view of semiconductor package 100 attached to a next level of assembly, such as a circuit board or printed circuit board (“PCB”). In accordance with the present embodiment, semiconductor package 100 comprises a substrate 110, such as a lead frame 110 and a substrate encapsulant 131, an electronic die 120, such as a semiconductor die 120, and package body 132. In one embodiment, substrate encapsulant 131 and package body 132 are configured as an encapsulant structure 130. In one embodiment, semiconductor die 120 can be an integrated circuit device, such as an analog device, a logic device, a mixed-signal device, a power device, a discrete device, a sensor device, an optical device, and/or a similar device as known to those of skill in the art.

In one embodiment, lead frame 110 includes a die pad 111 having a die pad top surface 111 b and an opposing die pad bottom surface 111 c. In one embodiment, die pad bottom surface 111 c comprises a continuous and substantially planar surface. Stated another way, die pad bottom surface 111 c is formed without, is absent, or is free of intentionally formed recessed portions or intentionally formed etched portions. In one embodiment, die pad 111 comprises a conductive material such as copper, a copper alloy, a plated material, combinations thereof, or other materials as known to those of skill in the art. In one embodiment, die pad 111 comprises a substantially rectangular plate shape having four sides and four corners, which may be rounded. It is understood that other shapes may be used as well. In some embodiments, the outer periphery of die pad 111 can be reduced in thickness using, for example, etching or stamping techniques.

In one embodiment, lead frame 110 further comprises a plurality of leads 112 spaced apart from die pad 111. Each lead 112 includes a lead top surface 112 b and an opposing lead bottom surface 112 c. In one embodiment, substrate encapsulant 131 encapsulates, covers, or encloses, for example, side portions of lead frame 110 except for portions that protrude outward from semiconductor package 100 as described hereinafter. Substrate encapsulant 131 includes a substrate top surface 131 a and an opposing substrate bottom surface 131 b. Semiconductor die 120 is electrically connected to die pad 111 and plurality of leads 112.

In accordance with the present embodiment, semiconductor package 100 is configured to have a die pad protrusion 111 a, which protrudes or extends outside or away from substrate bottom surface 131 b or the bottom surface of encapsulant 130. Die pad protrusion 111 a is configured to better facilitate the attachment of semiconductor package 100 to circuit board 10. More particularly, die pad protrusion 111 a provides both vertical surfaces and a horizontal surface for engaging an attachment structure, such as a solder ball 20 as illustrated, for example, in FIG. 1B. In some embodiments, die pad protrusion 111 a can have a thickness d1 of up to about 10 microns particularly if the height of semiconductor package is 100 is constrained. In other embodiments where package height or thickness is not constrained, thickness d1 can be less than about 25 microns. In accordance with the present embodiment, when semiconductor package 100 is attached to printed circuit board 10, die pad protrusion 111 a is configured to facilitate solder ball 20 surrounding the lateral surfaces or vertical surfaces of die pad protrusion 111 a in addition to its horizontal surface, which allows for semiconductor package 100 to be more stably and reliably connected to circuit board 10 or other assembly structures.

In one embodiment, plurality of leads 112 are spaced apart from the peripheral edge segments (e.g., four sides) of die pad 111 and can be arranged in directions perpendicular to the peripheral edge segments. Each lead 112 is further spaced apart from other leads 112 so that the leads are electrically disconnected from each other in some embodiments. It is understood that in some embodiments, some of the leads 112 can be electrically connected to each other depending on the system application. In accordance with the present embodiment, each of leads 112 includes a lead protrusion 112 a that protrudes or extends outside or away from substrate bottom surface 131 b or the bottom surface of encapsulant 130. In one embodiment, at least some of the lead protrusions 112 a are formed to have a similar shape as die pad protrusion 111 a. Lead protrusions 112 a protrude to a lower portion of each of the plurality of leads 112 and to the outside of semiconductor package 100 as generally illustrated in FIG. 1A. In accordance with the present embodiment, lead protrusions 112 a are configured to better facilitate the attachment of semiconductor package 100 to circuit board 10. More particularly, lead protrusions 112 a provide both vertical surfaces and horizontal surfaces for engaging attachment structures, such as solder balls 20 as illustrated, for example, in FIG. 1B. In some embodiments, lead protrusions 112 a can have a thickness dl of less than about 10 microns particularly if the height of semiconductor package is 100 is constrained. In other embodiments where package height is not constrained, thickness dl can be greater than about 10 microns. In accordance with the present embodiment, when semiconductor package 100 is attached to circuit board 10, lead protrusions 112 a are configured to facilitate solder ball 20 surrounding the vertical surfaces or lateral surfaces of lead protrusions 112 a in addition to their horizontal surfaces, which allows for semiconductor package 110 to be more stably and reliably connected to printed circuit board 10 or other assembly structures.

In some embodiments, semiconductor die 120 has a plate like shape and has a first surface 120 a and a second surface 120 b opposite to first surface 120 a. Semiconductor die 120 includes a plurality of conductive pads 121 formed on first surface 120 a. In some embodiments, semiconductor die 120 may include a protection layer (not shown) formed to cover the first surface 120 a of the semiconductor die 120 but leaving plurality of conductive pads 121 exposed to the outside. Plurality of conductive pads 121 can comprise aluminum, an aluminum alloy, copper, or other materials as known to those of skill in the art.

In accordance with the present embodiment, semiconductor die 120 is mounted on the lead frame 110 such that first surface 120 a and the plurality of conductive pads 121 face the top surface of lead frame 110 or substrate top surface 131 a. By way of example, conductive pads 121 can be attached or connected to lead frame 110 using a plurality of conductive bumps 122. In some embodiments, the width of semiconductor die 120 may be larger than the width of die pad 111 such that at least a portion of first surface 120 a overlaps at least portions of leads 112. In one embodiment, more than one conductive bump 122 connects semiconductor die 120 to die pad 111 as illustrated, for example, in FIGS. 1A and 1B.

Encapsulant 130 encapsulates lead frame 110 and semiconductor die 120 in order to protect exposed portions of lead frame 110 and semiconductor die 120 from external environments. In accordance with the present embodiment, encapsulant 130 includes a first encapsulant 131 or substrate encapsulant 131 encapsulating the lead frame 110 and a second encapsulant 132 or package body 132 encapsulating semiconductor die 120. Encapsulant 130 may be configured such that the first encapsulant 131 and the second encapsulant 132 are integrally formed.

Substrate encapsulant 131 encapsulates lateral surfaces of the lead frame 110 and is formed or provided to expose top and bottom surfaces of the lead frame 110 to the outside. In addition, substrate encapsulant 131 is formed or provided to expose die pad protrusion 111 a and lead protrusions 112 a of lead frame 110. In accordance with the present embodiment, die pad protrusion 111 a and lead protrusions 112 a are formed to protrude outward such that lead bottom surfaces 112 c and die pad bottom surface 111 c lie on a different plane than substrate bottom surface 131 b. Package body 132 encapsulates semiconductor die 120 adjacent to substrate top surface 112 b. In some embodiments, the side surfaces of substrate encapsulant 131 and the side surfaces of package body 132 are substantially coplanar.

With reference to FIG. 1B, semiconductor package 100 can be mounted or attached to a next level of assembly 10, such as circuit board 10. In one embodiment, circuit board 10 comprises a circuit pattern 11 electrically connected to lead frame 110 of semiconductor package 100 using conductive connective structures 20, such as solder balls 20. In one embodiment, solder balls 20 are connected between circuit pattern 11 and die pad protrusion 111 a of lead frame 110 and between circuit pattern 11 and lead protrusions 112 a. In accordance with the present embodiment, solder balls 20 are connected to circuit pattern 11 so as to surround the lateral surfaces or vertical surfaces of die pad protrusion 111 a and lead protrusions 112 a. These attributes facilitate semiconductor package 100 being more stably connected to circuit board 10, thereby improving reliability of the assembly structure. In one embodiment, a first solder structure electrically connects die pad bottom surface 111 c to a first portion circuit pattern 11 and a second solder structure electrically connects a lead 112 to a second portion of circuit pattern 11, wherein the first solder structure has a greater width than the second solder structure as illustrated, for example, in FIG. 1B. In one embodiment, the first solder structure extends entirely across die pad bottom surface 111 c as generally illustrated, for example, in FIG. 1B. In a further embodiment, the first solder structure surrounds lateral surfaces of the die pad protruding from the substrate bottom surface, and the second solder structure surrounds lateral surfaces of one of the plurality of leads protruding from the substrate bottom surface.

In some embodiments, solder balls 20 connecting semiconductor package 100 to circuit board 10 have a thickness d2 of about 150 microns or less. In some embodiments, solder balls 20 can be made of conductive materials, such a tin/lead, leadless tin, and other similar materials as known to those of skill in the art.

In summary, semiconductor package 100 according to the present embodiment comprises die pad protrusion 111 a and lead protrusions 112 a protruding to the outside of semiconductor package 100. These protrusions better facilitate using conductive structures, such as solder balls 20 to electrically connect semiconductor package 100 to a next level of assembly, such as circuit board 10. In accordance with the present embodiment, the conductive structures surrounds the lateral surfaces of die pad protrusion 111 a and lead protrusions 112 a to provide a more stable physical and electrical connection between semiconductor package 100 and circuit board 10 thereby improving the reliability of the assembled structure (i.e., board-level reliability).

FIG. 2A illustrates a cross-sectional view of an electronic package 200 or electronic package structure 200, such as a semiconductor package 200 in accordance with another embodiment. FIG. 2B illustrates a cross-sectional view of electronic package 200 attached to a next level of assembly, such as circuit board 10. In some embodiments, semiconductor package 200 includes a substrate 210, such as a lead frame 210 and substrate encapsulant 131, electronic die 120, such as semiconductor die 120, and package body 132. In one embodiment, substrate encapsulant 131 and package body 132 are configured as an encapsulant structure 130. In one embodiment, substrate encapsulant 131 encapsulates, covers, or encloses, for example, side portions of lead frame 210. Substrate encapsulant 131 includes a substrate top surface 131 a and an opposing substrate bottom surface 131 b. Semiconductor package 200 is similar to semiconductor package 100 illustrated in FIGS. 1A and 1B. Thus, the following description will focus more on differences between semiconductor package 100 and semiconductor package 200.

In one embodiment, lead frame 210 includes a die pad 211 having a die pad top surface 21 la and an opposing die pad bottom surface 211 b, a plurality of leads 212 each having a lead top surface 212 a and an opposing lead bottom surface 212 b, and a plurality of conductive bumps 213 disposed on die pad bottom surface 211 b and lead bottom surfaces 212 b. In one embodiment, a portion of die pad bottom surface 211 b is formed having a plurality of pad portions 211 c separated by one or more recesses. Stated another way, die pad bottom surface 211 b is intentionally formed with a plurality of recessed portions such that die pad bottom surface 211 b is not a continuous or substantially planar surface in contrast to die pad bottom surface 111 c illustrated, for example, in FIG. 1A. In accordance with the present embodiment, the recess between pad portions 211 c is encapsulated by substrate encapsulant 131. In one embodiment, parts of die pad bottom surface 211 b and lead bottom surfaces 212 b are substantially co-planar the substrate encapsulant bottom surface 131 b or the bottom surface of encapsulant 130 as illustrated, for example, in FIG. 2A.

In accordance with the present embodiment, pad portions 211 c are exposed to the outside of semiconductor package 200 and a conductive bump 213 is disposed on or adjacent the exposed die pad bottom surface 211 b of pad portions 211 c. In one embodiment, a conductive bump 231 is disposed on each pad portion 211 c of die pad 211. Stated another way, die pad 211 includes a plurality of conductive bumps 213 disposed along die pad bottom surface 211 b. In some embodiments, conductive bumps 213 can be a solder or other similar materials. In accordance with the present embodiment, conductive bumps 213 are formed in a solder-on-pad (SOP) type configuration. In one embodiment, die pad 211 comprises a conductive material such as copper, a copper alloy, a plated material, combinations thereof, or other materials as known to those of skill in the art.

In one embodiment, die pad 211 comprises a substantially rectangular plate shape having four sides and four corners, which may be rounded. It is understood that other shapes may be used as well. In some embodiments, the outer periphery of die pad 211 can be reduced in thickness using, for example, etching or stamping techniques. In accordance with the present embodiment, semiconductor die 120 is electrically connected to die pad 211 and plurality of leads 212 using, for example, conductive bumps 122. In one embodiment, more than on conductive bump 122 is used to electrically connect semiconductor die 120 to die pad 211.

In one embodiment, plurality of leads 212 are spaced apart from the peripheral edge segments (e.g., four sides) of die pad 211 and can arranged in directions perpendicular to the peripheral edge segments. Each lead 212 is further spaced apart from other leads 212 so that the leads are electrically disconnected from each other in some embodiments. It is understood that in other embodiments, some of the leads 212 can be electrically connected to each other in accordance with the requirements of a particular system application. In accordance with the present embodiment, each lead bottom surface 212 b is exposed to the outside of semiconductor package 200 and includes a conductive bump 213 disposed on the exposed lead bottom surface 212 b surface as illustrated, for example, in FIG. 2A.

In accordance with the present embodiment, conductive bumps 213 are placed onto lead frame 210 prior to semiconductor package 200 being attached to circuit board 10 with solder balls 20 so that solder balls 20 are not directly attached to lead frame 210 as in previous package structures. In one embodiment, conductive bumps 213 and solder balls 20 preferably comprise the same material. In other embodiments, conductive bumps 213 and solder balls 20 may comprise different materials. In accordance with the present embodiment, by placing conductive bumps 213 onto lead frame 210 before attaching semiconductor package 200 to a next level of assembly, semiconductor package 200 can be more easily and firmly attached or connected to circuit board 10. This attribute provides for a more stable assembled structure, which further improves reliability. In an alternative embodiment, solder balls 20 can be advantageously attached to conductive bumps 213 prior to or in advance of the attachment of semiconductor package 200 to the next level of assembly. In some embodiments, solder balls 20 can have a thickness d3 of about 200 microns or less.

FIG. 3A illustrates a perspective plan view of an electronic package 300 or electronic package structure 300, such as a semiconductor package 300 in accordance with a further embodiment. FIG. 3B illustrates a partial cross-sectional view of semiconductor package 300 taken along reference line 1-1′ of FIG. 3A. As illustrated in FIG. 3B, semiconductor package 300 can be attached to, for example, a next level of assembly, such as circuit board 10. In accordance with the present embodiment, semiconductor package 300 comprises a substrate 310, such as lead frame 310 and substrate encapsulant 131, semiconductor die 120, and package body 132. In one embodiment, substrate encapsulant 131 and package body 132 are configured as an encapsulant structure 130. Semiconductor package 300 is similar to semiconductor package 100 and semiconductor package 200 and the following description will focus more on the differences between semiconductor package 300 and semiconductor package 100 and semiconductor package 200.

Lead frame 310 includes a die pad 311 having a die pad top surface 311 a and an opposing die pad bottom surface 311 b. In one embodiment, die pad 311 comprises a substantially rectangular plate shape having four sides and four corners, which may be rounded. It is understood that other shapes may be used as well. In some embodiments, the outer periphery of die pad 311 can be reduced in thickness using, for example, etching or stamping techniques. In one embodiment, die pad 311 comprises a conductive material such as copper, a copper alloy, a plated material, combinations thereof, or other materials as known to those of skill in the art.

Lead frame 310 further comprises a plurality of leads 312 spaced apart from die pad 311. In one embodiment, plurality of leads 312 are spaced apart from the peripheral edge segments (e.g., four sides) of die pad 311 and can be arranged in directions perpendicular to the peripheral edge segments. Each lead 312 is further spaced apart from other leads 312 so that the leads are electrically disconnected from each other in some embodiments. It is understood that in other embodiments, some of leads 312 can be electrically connected to each other depending on the requirements of a specific system application. In accordance with the present embodiment, each lead 312 includes a first lead portion 312 a and a second lead portion 312 b extending laterally away from first lead portion 312 a. In accordance with the present embodiment, second lead portion 312 b has a lower portion reduced in thickness. In one embodiment, the lower portions of second lead portions 312 b are half etched. In accordance with the present embodiment, first lead portion 312 a includes a lead bottom surface 312 c exposed to the outside of semiconductor package 300 and second lead portion 312 b includes a lead top surface 312 d configured to attach to or electrically connect with semiconductor die 120. In one embodiment, first lead portion 312 a is positioned at an outermost part of lead frame 310 and lead bottom surface 312 c of first lead portion 312 a is exposed to the outside of semiconductor package 300. In one embodiment, lead bottom surface 312 c of first lead portion 312 a is a portion or surface configured to connect to conductive structure 20 or solder ball 20 when semiconductor package 300 is assembled with or attached to circuit board 10.

Second lead portions 312 b are formed to extend from first lead portions 312 a towards die pad 311. Since the lower portion of each second lead portion 312 b is reduced in thickness and filled, encapsulated, or covered by encapsulant 130, such as substrate encapsulant 131, second lead portion 312 b is not exposed to the outside of semiconductor package 300. Stated another way, the lower portion of each second lead portion 312 b is encapsulated by substrate encapsulant 131 or encapsulant structure 130. In accordance with the present embodiment, semiconductor die 120 is attached to lead top surface 312 d of second lead portion 312 b. In one embodiment, conductive pads 121 on semiconductor die 120 are electrically connected to second lead portions 312 b and die pad top surface 311 a with conductive bumps 122. In accordance with the present embodiment, semiconductor die 120 is positioned to overlap second lead portion 312 b but does not overlap first lead portion 312 a. Stated another way, peripheral surfaces 120 c of semiconductor die 120 are positioned on second lead portions 312 b, but peripheral surfaces 120 c do not overlap first lead portions 312 a.

In accordance with the present embodiment, a first connection point P1, at which each of the plurality of leads 312 and the circuit board 10 are connected to each other, is positioned on lead bottom surface 312 c of first lead portion 312 a, and a second connection point P2, at which each of the plurality of leads 312 and the semiconductor die 120 are connected to each other, is positioned on lead top surface 312 d of each second lead portion 312 b. Stated another way, the first connection point P1 and the second connection point P2 are positioned to be laterally separated from each other. As described previously, the first connection point P1, at which each of plurality of leads 312 and circuit board 10 are connected to each other, and the second connection point P2, at which each of the plurality of leads 312 and the semiconductor die 120 are connected to each other, are positioned so as to not overlap each other, thereby attaining improved results in assembled structure reliability tests.

For example, in a case of a conventional semiconductor package in which the first connection point P1 and the second connection point P2 overlap each other, the conventional semiconductor package demonstrated 598 cycles of temperature circulation endurance during board level reliability tests. However, in a case of semiconductor package 300 according to the present embodiment where the first connection point P1 and the second connection point P2 do not overlap each other, semiconductor package 300 demonstrated 1104 cycles of temperature circulation endurance, which is about twice the temperature circulation endurance of the conventional package.

A temperature circulation endurance of a semiconductor package structure is tested by placing a semiconductor package in an enclosed chamber and investigating whether the semiconductor package is distorted or not while raising the temperature of the chamber to the highest temperature or lowering the temperature of the chamber to the lowest temperature at regular intervals. In addition, a cycle typically corresponds to a measurement period in which the internal temperature of the chamber is raised from a reference temperature (e.g., room temperature) to the highest temperature and is lowered to the lowest temperature to then be raised to the reference temperature.

In one embodiment, second lead portions 312 b are angled with respect to first lead portions 312 b as illustrated in FIG. 3A in order to accommodate I/O pad layout configurations on semiconductor die 120. In addition, in one embodiment one or more second lead portions 312 b are of a different size or lateral width compared to other second lead portions 312 b as illustrated in FIG. 3A in order to accommodate more than one I/O pad on semiconductor die 120.

In summary, in semiconductor package 300 first connection point P1, where each of the plurality of leads 312 and the circuit board 10 are connected to each other, and the second connection point P1, where each of the plurality of leads 312 and the semiconductor die 120 are connected to each other, are positioned so as not to overlap each other, thereby improving the board level reliability of semiconductor package 300.

It is understood that the features of semiconductor package 300 can be applied to semiconductor packages 100 and 200 described previously. Also, the features of semiconductor package 100 can be applied to either semiconductor package 200 or 300 or the features can be combined together in one semiconductor package.

In view of all of the above, it is evident that a novel structure and method is disclosed. Included, among other features, are protrusion structures, conductive bump structures, and/or connection point structures configured to improve the board level or assembled structure reliability. More particularly, the features described herein singularly or in various combinations reduce board level failures resulting from temperature circulation endurance tests, as well as others.

While the present invention has been particularly illustrated and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details can be made therein without departing from the spirit and scope of the present invention as defined by the following claims. By way of example, the semiconductor packages can be configured as multi-chip packages. It is therefore desired that the present embodiments be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than the foregoing description to indicate the scope of the invention.

As the claims hereinafter reflect, inventive aspects may lie in less than all features of a single foregoing disclosed embodiment. Thus, the hereinafter expressed claims are hereby expressly incorporated into this Detailed Description of the Drawings, with each claim standing on its own as a separate embodiment of the invention. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and meant to form different embodiments as would be understood by those skilled in the art. 

What is claimed is:
 1. An electronic package structure comprising: a substrate comprising: a die pad having a die pad top surface and an opposing die pad bottom surface, wherein the die pad comprises a conductive material; a plurality of leads laterally spaced apart from the die pad; and a substrate encapsulant interposed between the die pad and the plurality of leads, wherein the substrate encapsulant has a substrate top surface and an opposing substrate bottom surface, and wherein the die pad and the plurality of leads protrude outward from the substrate bottom surface; an electronic die having a first major surface and a second major surface opposite to the first major surface and a pair of opposing outer edges in cross-sectional view, wherein the first major surface of the electronic die is spaced apart from the die pad top surface and upper surfaces of the plurality leads, and wherein the outer edges overlap a pair of leads in the cross-sectional view, and wherein the electronic die is electrically coupled to the die pad and the plurality of leads; and a package body encapsulating the electronic die and the substrate top surface, wherein the substrate bottom surface is exposed to the outside.
 2. The structure of claim 1, wherein the die pad bottom surface comprises a continuous and substantially planar surface.
 3. The structure of claim 1, wherein the die pad bottom surface and bottom surfaces of the leads protrude outward a distance of less than about 10 microns from the substrate bottom surface.
 4. The structure of claim 1 further comprising a circuit board electrically connected to the substrate through solder structures and having a circuit pattern formed thereon.
 5. The structure of claim 4, wherein: the die pad bottom surface comprises a continuous and substantially planar surface; a first solder structure electrically connects the die pad bottom surface to a first portion the circuit pattern; and a second solder structure electrically connects a lead to a second portion of the circuit pattern, wherein the first solder structure has a greater width than the second solder structure.
 6. The structure of claim 5, wherein the first solder structure extends entirely across the die pad bottom surface.
 7. The structure of claim 4, wherein: a first solder structure surrounds vertical side surfaces of the die pad protruding from the substrate bottom surface; and a second solder structure surrounds vertical side surfaces of one of the plurality of leads protruding from the substrate bottom surface.
 8. The structure of claim 4, wherein the plurality of leads comprises: a first lead portion exposed to the outside of the substrate bottom surface and attached to the circuit pattern at a first connection point; and a second lead portion laterally extending towards the die pad and having a recessed bottom surface encapsulated by the substrate encapsulant, and wherein a conductive pad on the electronic die is attached to the second lead portion at a second connection point, and wherein the first connection point is laterally separated from the second connection point, and wherein the electronic die overlaps the second connection point but not the first connection point.
 9. The structure of claim 1, wherein: the electronic die comprises a plurality of conductive pads on the first major surface; the plurality of conductive pads are electrically coupled to the plurality of leads and the die pad with conductive bumps; and more than one conductive bump connects the electronic die to the die pad.
 10. An electronic package structure comprising: a substrate comprising: a die pad having a die pad top surface and an opposing die pad bottom surface, wherein the die pad comprises a conductive material; a plurality of leads laterally spaced apart from the die pad each lead having a lead top surface and an opposing lead bottom surface; a substrate encapsulant interposed between the die pad and the plurality of leads, wherein the substrate encapsulant has a substrate top surface and an opposing substrate bottom surface; an electronic die electrically coupled to the die pad and the plurality of leads; and a package body encapsulating the electronic die and the substrate top surface, wherein the substrate bottom surface is exposed to the outside, and wherein the substrate further comprises one or more structural features configured to improve board-level reliability, the one or more features comprising one or more of: the die pad and the plurality of leads configured to protrude outward from the substrate bottom surface such that side surfaces of the die pad and the plurality of leads are exposed to the outside, conductive bumps disposed on the die pad bottom surface and the lead bottom surfaces, or at least one lead comprising: a first lead portion exposed to the outside of the substrate bottom surface and defining a first connection point for attaching the electronic package structure to a next level of assembly; and a second lead portion laterally extending towards the die pad and having a recessed bottom surface encapsulated by the substrate encapsulant, the second lead portion defining a second connection point for attaching to the electronic die, wherein the first connection point is laterally separated from the second connection point.
 11. The structure of claim 10, wherein the one or more features includes the conductive bumps, and wherein the die pad bottom surface comprises a plurality of pad portions separated by a recess encapsulated by the substrate encapsulant.
 12. The structure of claim 11, wherein the die pad bottom surface and lead bottom surfaces are substantially co-planar with the substrate bottom surface, and wherein a conductive bump is disposed on each pad portion.
 13. The structure of claim 10, wherein the one or more features includes the die pad and the plurality of leads configured to protrude outward from the substrate bottom surface, and wherein the die pad bottom surface comprises a continuous and substantially planar surface.
 14. The structure of claim 10, wherein the one or more features includes the at least one lead comprising the first lead portion and the second lead portion, wherein a conductive pad on the electronic die is attached to the second lead portion at the second connection point, and wherein the electronic die overlaps the second connection point but not the first connection point.
 15. The structure of claim 10, wherein: the electronic die comprises a plurality of conductive pads on a major surface; the plurality of conductive pads are electrically coupled to the plurality of leads and the die pad with conductive bumps; and more than one conductive bump connects the electronic die to the die pad.
 16. An electronic package structure comprising: a substrate including a die pad and a plurality of leads spaced apart from the die pad; an electronic die electrically connected to the die pad and the plurality of leads; and an encapsulant structure encapsulating the substrate and the electronic die, wherein a bottom surface of the die pad and bottom surfaces of the plurality of leads are exposed to the outside, wherein the electronic die is attached to first portions of the plurality of leads with conductive bumps to define first connection points, and wherein the plurality of leads comprise second portions integral with the first portions, wherein the second portions are configured to define second connection points for attaching to a next level of assembly, and wherein the first connection points and the second connection points are laterally separated, and wherein the electronic die has an edge laterally interposed between one of the first connection points on a first lead and one of the second connection points on the first lead.
 17. The structure of claim 16, wherein the first portions of the plurality of leads are enclosed within the encapsulant structure, and wherein the first portions are angled with respect to the second portions, and wherein at least one first portion has a larger width than another first portion.
 18. The structure of claim 16, wherein the substrate further comprises a substrate encapsulant interposed between the die pad and the plurality of leads, and wherein the substrate encapsulant has a substrate top surface and an opposing substrate bottom surface, and wherein the die pad bottom surface and the bottom surfaces of the leads are exposed in the substrate bottom surface.
 19. The structure of claim 18, wherein the die pad bottom surface and the bottom surfaces of the leads protrude outward from the substrate bottom surface to provide lateral surfaces configured to engage solder structures along side surfaces of the die pad and leads.
 20. The structure of claim 19, wherein the die pad bottom surface comprises a continuous and substantially planar surface. 